有机锂化合物中化学键的性质——-反式1,2-二锂代乙烷、1,2-二锂代乙烯和1,2-二锂代乙炔分子中化学键的abinitio研究

用从头计算法计算了电荷密度图和各价分子轨道的键强参数.结果表明,三个标题化合物的稳定构型都存在双桥式四中心键.追其原因是:这种构型有利于Li的2p轨道的吸电子效应,这种效应可使C—Li键增强.此外,也发现这三个化合物中C—C键的强度大于C=C键,而后者又比C≡C键为强.本文亦讨论了这种“反常”的原因.     

烷基锂分子中化学键的 ab initio 研究

本文用6-13G基函对3-12G基优化构型进行单点ab initio (从头计算法) 计算, 并根据轨道的组合系数、电荷密度图和键强参数等详尽地分析了烷基锂分子的成键情况。烷基锂的易挥发、易聚合、聚合物易溶于烃类溶剂中等物理、化学性质主要是其C－Li键具有显著的共价性缘故。由于烷基锂的C-Li键比C－H和C－C键的强度要小,故C-Li键易于断裂,使烷基锂表现有高的化学反应活性。     

(R)-N-乙酰基-四氢噻唑-2-硫酮-4-甲酰TT的合成及其晶体结构

由N-乙酰(R)-四氢噻唑-2-硫酮-4-羧酸在三聚氯氰及三乙胺存在下与四氢噻唑-2-硫酮反应得到标题化合物，[α]^2^0~D +11.18°。用X射线衍射法测得其晶体结构，属单斜晶系，空间群为P2~1/c。晶体学数据：a=0.9959(4)nm，b=1.1469(4)nm，c=1.1108(3)nm，β=92.72(3)°，V=1.2673(8)nm^3，Z=4。分子中两个C=O基，两个C=S基团处于C(1)-N(1)-C(4)及C(6)-N(2)-C(7)键两侧呈反式。用PM3分子轨道方法研究了该化合物的电子结构，电荷和键序分布，得到该化合物前线轨道性质。     

平面型1,1-二锂代环丙烷比四面体型稳定的原因

在3-21G/Dunning基水平的量子化学"从头计算"基础上,绘制平面型1,1-二锂代环丙烷(PDCP)的A~1及B~2对称块中各分子轨道的波函数等值线图及PDCP和TDCP (四面体型)B~1和A~2对称块中各分子轨道示意图,并且求出PDCP及TDCP中各价电子i对于各种键A-B的f~i,A-B值.得到结论:由f~i,A-B所得定量结论与上述两种图形所得定性结论是完全一致的.再一次证明用f~i,A-B定量表达i价电子对A-B键中结合力贡献的合理性.把这些图与f~i,A-B数据结合起来分析,可和是结论:PDCP比TDCP稳定的主要原因在于前者的几何条件有利于A~1中σ-σ、B~2中σ-pscudo-π和B~1及A~2中π-π共轭效应的发生,使得PDCP中(C(1)-Li键远强于TDCP中的C(1)-Li键.     

吗啉二硫代氨基甲酸铁（III）配合物Fe(S_2CNC_4H_8O)_3的合成、表征及晶体结构

合成了标题化合物Fe(S_2CNC_4H_8O)_3，得到黑色柱状晶体。晶体属三斜晶系 ，空间群为P－1，晶胞参数a=0.9300(2)nm，b=1.0490(2)nm，c=1.3710(3)nm， a=100.60(3)，γ=106.60(3)，V=1.2445(4) nm~3，M_r=542.58，Z＝2。中心Fe原 子分别来自三个吗啉二硫代氨基甲酸的六个硫原子配位形成八面体构型，由于四元 螯合环的环张力，导致该八面体严重变形，六个Fe-S键的键长范围在0.2423(5)～ 0.2458(2)nm。热分析表明标题化合物在791.80 ℃完成分解。     

碳氢化合物中化学键的键能和键热

本文根据五个标准化合物来规定 C—H,C—C,C(?)C,C=C 和 C≡C 键的键能和键热。然后把第二种相互作用分为四大类,分别按照结构特征给予校正值,并从理论上分析和讨论了这些校正值的物理意义。从提出的键能、键热和校正值的数值计算了202个各种类型的碳氢化合物的原子生成热,结果90%以上的化合物的误差不超过1千卡/克分子,只有一个分子的误差大于2千卡/克分子。最后还讨论了用标准键能和标准键热来代替键能和键热,以避免由于β-石墨升华热尚未确定所引起的困难。     

反-1,2-双[2'-(5'-苯基恶唑基)]乙烯的晶体结构

用X射线单晶衍射法测定了反-1,2-双[2'-(5'-苯基恶唑基)]乙烯(POEOP)的晶体结构,POEOP晶体属单斜晶系, 空间群为P2~1/C, a=0.8268(2), b=0.5977(2), c=1.6292(3)nm;β=100.55(2)°; v=0.7915nm~3; Z=2; d~x=1.319g/cm~3。POEOP分子具有中心对称性,它的两个苯环和两个恶唑环是彼此平行的, 但整个分子却稍有些扭曲成螺旋浆式构型。键长数据表明POEOP分子中苯环与恶唑环以及恶唑环与C'=C双键间均有很大程度共轭。     

某些镧系化合物化学键特性的INDO研究

本文用INDO方法研究了不同价态镧系化合物的成键性质和4f轨道在成键中的作用,结果表明,镧系化合物的成键受许多因素,如价态、半径、配体、配位数、空间构型等影响。不同配体与镧系元素成键的强度差别较大;高价态的共价性大于低价态的;配位数低的大于配位数高的。某些特殊构型的镧系化合物除σ键外,还形成重叠较好的π配键,使Ln—L键共价性大大增强。4f轨道在成键中的作用比5d的少得多,三价(二价态)的4f轨道基本定域(<0.1％),四价态的4f轨道对成键的贡献明显增大,可接近1％。     

有机氟化合物量子化学研究 I: 二氟乙炔分子中化学键特性的从头计算

实验发现, F-C≡C-F与H-C≡C-H相比, 其C≡C三重键的离解能要小250.8kJ/mol,而该键的键长却比C~2H~2的短。这与"键越短键就越强"的传统看法不一致。我们通过从头计算研究, 发现主要原因是C~2F~2分子中F原子的孤对电子对C≡C三重键起反键作用, 从而削弱了C≡C三重键的强度; F原子的吸电子性又使C的原子轨道收缩效应增强,而使得C≡C三重键变短。     

有机氟化合物量子化学研究 I: 二氟乙炔分子中化学键特性的从头计算

实验发现, F-C≡C-F与H-C≡C-H相比, 其C≡C三重键的离解能要小250.8kJ/mol,而该键的键长却比C~2H~2的短。这与"键越短键就越强"的传统看法不一致。我们通过从头计算研究, 发现主要原因是C~2F~2分子中F原子的孤对电子对C≡C三重键起反键作用, 从而削弱了C≡C三重键的强度; F原子的吸电子性又使C的原子轨道收缩效应增强,而使得C≡C三重键变短。     

稀土夹心化合物的SCF-Xａ-SW研究 2:Cp~2Yb C~2H~2和Cp~2Yb(OC)~2

用SCF-Xａ-SW方法非相对论和相对论方案计算了Cp~aYb C~2H~2和Cp~2Yb(OC)~2.非相对论主HOMO是Cp的π轨道,相对论间接效应的作用,使得Yb的4f轨道能级上升为HOMO,相对论结果与Yb二价化合物不稳定、易氧化的实验结果一致,也表明了研究重稀土化合物考虑相对论效应的必要性.计算共价键强度与Cp~2Yb相近,比YbF~3和Cp~3SM弱,再次表明二价稀土化合共价键比三价化合物弱.同时也证实了σ型配体(CO)与稀土元素的配 位作用比π型配体(C~2H~2)强的结论.     

Intramolecular hydrogen bonding of novel o-hydroxythioacetophenones and related compounds evaluated by deuterium isotope effects on 13C chemical shifts

A new class of compounds, the 2-hydroxythioacetophenones, and related compounds have recently been synthesized. The hydrogen-bond system has been characterized by NMR chemical shifts and deuterium isotope effects on these as well as by DFT calculations. Use of solid-state (13)C NMR has enabled measurements of the intrinsic deuterium isotope effects of the most abundant tautomer of beta-thioxoketones. The compounds show very interesting long-range deuterium isotope effects on the thiocarbonyl carbon. The intramolecular hydrogen bonds of o-hydroxythioacetophenones are found to be slightly stronger than those of the corresponding acetophenones. The reactivity and stability of the compounds can be related to hydrogen bonding and to the presence of electron donating substituents.     

反-1,2-双[2-(5-取代苯基恶唑基)]环丙烷的合成与光性能的研究

合成了8个反 -1,2-双[2-(5-取代苯基恶唑基)]环丙烷和2个1,2-双[2-取代苯基恶唑基)]乙烷,其中9个为新化合物.讨论了化合物的结构与其电子光谱及荧光量子产率间的关系.发现恶唑环与三元环间存在一定程度的共轭,并解释了上述化合物荧光量子产率较低的现象.     

Role of the chemical structure of metal–organic framework compounds in the adsorption of hydrogen

The effect of the chemical structure of metal–organic framework compounds (MOF) (the presence of coordination-unsaturated metal ions, the nature of the metal ions, the presence of electron donor and electron acceptor groups in the ligands) on the ability of such compounds to sorb hydrogen is examined. It is shown that the macroscopic parameters (the surface area and pore size) make a major contribution to the adsorption of hydrogen while the chemical structure of the MOF plays a subsidiary role by determining the structural characteristics of the adsorbent.     

Cation-radicals in the electrochemical oxidation of 1,2,6-trimethyl-3,5-diacetyl-1,2-dihydropyridines

The ESR spectra of the cation-radicals of 4-substituted 3,5-diacetyl-1,2,6-trimethyl-1,2-dihydropyridines were generated electrochemically by oxidation in acetonitrile at –40°C. The unpaired electron distribution in the cation-radicals was established by analysis of the hyperfine structure of the ESR spectra. It was found that the size of the electrochemical oxidation potential of the compounds and the unpaired electron distribution in the cation-radical were subject to the inductive effect of the substituents in positions 3 and 5 of the heterocycle.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 772–775, June, 1997.     

金属多硫1,2-二硫烯配合物C[Ni(dmid)~2]的研究

首次制得通式为C[Ni(dmid)~2]系列新配位化合物(C为外部阳离子,H~2dmid=4,5-二硫醇-1,3-二硫-2-酮)。当这些配合物用化学法氧化时,得到同一种配合物[Ni(dmid)~2],并确定了这些新配合物的组成,研究了它们的IR,UV,ESR,XPS谱和循环伏安图,测定了室温导电率。XPS谱的研究结果说明,用化学法氧化时电子转移过程主要发生在配体上,配位体的电荷分布发生了变化。     

Interlaboratory comparison of limits of detectic in negative chemical ionization mass spectrometry

Data are presented on the limits of detection for a series of nine compounds in negative chemical ionization (NCI) mass spectra obtained in five different mass spectrometers: Finnigan 4000 with a 4500 ion source, Kratos MS-80, Hewlett-Packard 5985 and two Finnigan 4500s. The nine compounds undergo either resonance capture or dissociative capture of an electron at optimum energies ranging from 0.0 to 1.1 eV. The limits of detection generally increased with increasing optimum electron energy. The limit of detection as a function of optimum electron capture energy is expected to provide information about the electron energy distribution in the ion sources. The data showed scatter within and between instruments. The scatter is believed to be due primarily to reactions with low levels of adventitious gases such as oxygen in the ion source. The data also suggested wide variations in electron energies between the instruments. The variation in the electron energy distribution is thought to have been caused by variations in the ion optical fields within the instruments. These results suggest that the requirements for reproducibility in NCI mass spectra at the limit of detection are rigorous control of trace gases in the ion source, control of the electric fields within the source including ion optical fields that penetrate the source aperture control of pressure, temperature and other factors that influence NCI mass spectra.     

对羟基苯甲酸、水杨酸分子印迹聚合物分子识别性质的 研究

以对羟基苯甲酸(4-HBA)为模板分子,4-乙烯吡啶(4-Vpy)为功能单体,制备得到了4-HBA分子印迹聚合物P(4-HBA),研究了该聚合物的分子识别机理,并与在同样条件下制备的水杨酸(SA)分子印迹聚合物P(SA)进行了分子识别能力的比较。结果表明：P(SA)比P(4-HBA)具有更好的分子识别能力。这是由于SA的酸性较4-HBA强,因此与碱性功能单体4-Vpy之间的静电作用更强,从而得到的复合物更稳定。本实验结果证明：功能单体与模板分子形成稳定的复合物是得到分子识别能力高的模板聚合物的前提条件。本文将有助于对分子印迹的过程以及分子印迹聚合物分子识别机理的进一步理解,并且对于根据模板分子的性质预测MIP的分子识别能力也将具有一定的指导意义。     

Strong dissimilarities between the gas-phase acidities of saturated and alpha,beta-unsaturated boranes and the corresponding alanes and gallanes

The effect that unsaturation has on the intrinsic acidity of boranes, alanes, and gallanes, was analyzed by B3 LYP and CCSD(T)/6-311+G(3df,2p) calculations on methyl-, ethyl-, vinyl-, and ethynylboranes, -alanes and -gallanes, and on the corresponding hydrides XH3. Quite unexpectedly, methylborane, which behaves as a carbon acid, is predicted to have an intrinsic acidity almost 200 kJ mol(-1) stronger than BH3, reflecting the large reinforcement of the C--B bond, which upon deprotonation becomes a double bond through the donation of the lone pair created on the carbon atom into the empty p orbital of the boron. Also unexpectedly, and for the same reason, the saturated and alpha,beta-unsaturated boranes are much stronger acids than the corresponding hydrocarbons, in spite of being carbon acids as well. The Al derivatives also behave as carbon acids, but in this case the most favorable deprotonation process occurs at C beta, leading to the formation of rather stable three-membered rings, again through the donation of the C beta lone pair into the empty p orbital of Al. For Ga-containing compounds the deprotonation of the GaH2 group is the most favorable process. Therefore only Ga derivatives behave similarly to the analogues of Groups 14, 15, and 16 of the periodic table, and the saturated derivatives exhibit a weaker acidity than the unsaturated ones. Within Group 13, boranes are stronger acids than alanes and gallanes. For ethyl and vinyl derivatives, alanes are stronger acids than gallanes. We have shown, for the first time, that acidity enhancement for primary heterocompounds is not only dictated by the position of the heteroatom in the periodic table and the nature of the substituent, but also by the bonding rearrangements triggered by the deprotonation of the neutral acid.